Sources:http://www.stepmania.com/stepmania/readme.php - StepManiareadme, including SM file specifications.
http://www.geocities.com/moon_jihad/smtute.html - A nice tutorial on making an SM file.
http://www.ajworld.net/simfile_types.txt - The be all, end all of step file information. I found this during my research and lost my will to go all-out in this writeup, because someone already had and knew ten times as much as I. I'm so depressed.